Watch timing apparatus



`ulne 16, 1942. T, B GlBBs 2,286,907`

WATCH TIMING APPARATUS Filed June 17, 1937 7 4 Sheets-Sheet 1 June 16, 1942. T'. B. cslBBs A WATCH TIMING APPARATUS Filed June 17, 1 93'7 4 Sheets-Sheet 2 ffazf/"cfafOfl Thomas E. GQ'S June 16, 1942. T, Q @|555 2,286,907

WATCH TIMING APPARATUS Filed June 1'7, 1937 4 Sheets-Sheet 3 Julie 16, 1942. T, B. GIBBS WATCH TIMING APARATUS 4 sheets-shew 4 Filed June 17,v 1937 Patented June 16.,l 1942 d UNITED STATES PATENT oFFicE WATCH TIMING APPARATUS Thomas B. Gibbs, Chicago, lll.

Application June 17,1937, serial No. 148,747

8 Claims.

y controlled by a master watch, and means for villuminating the dialintermittently responsive to the ticks o r beats of the Watch under test.l

While the abovedescribed apparatus has given good satisfaction, it has several objectionable features, `among which may be mentioned the fact that it can only be used at points where regulated 60-cycle power is available. Y lscopic principle, moreover, is not whollysuited 11o watch timing, as the beat frequency o`f arwatch is so low that flicker is present, which is a strain onthe eyes of the operator.

The object of the present invention Vtherefore is to produce a new and improved watch timing apparatus which is free from the objectionable features of prior apparatus of thischaracter.

More'in particular, an object of the invention is to produce a watch timing apparatus which is not dependent on the frequency of the power supply and which can be arranged to operate from any commercial power source, whether A. C. or D. C.

A further specic object of the invention is tov produce a watch timing apparatus in which the stroboscopic principle is dispensed with, and in which a new and improved arrangement is employed for comparing a watch under-'test' with a master watch or other standard frequency source.

An Vincidental object is to provide a standard frequency generator using a master watch as a primary constant frequency, source and having a fio-cycle or other desired frequency output with sufiicient power so that theY same can be usedy to operate a synchronous motor. A

`The fior'egoing and other features of the invention 'will be pointed out more i`n detail in the course QI. the description of the invention which followsfreference being had to the accompanying drawings, in which- Fig. 1 is a front view of the mechanical partof the apparatus, referred to hereinafter as a timer; Fig. 2 isa top view, on a larger scale, of the timer` shown in Fig. 1, with the cover of the outside casing removed;

Fig. 3 is a side view of the timer, Awith the casing in section;

Fig. 4 is a partial section on the line 4 6, Fig. 2, showing the motor starting device;

` Fig. 5 is a section on the line 5 5, Fig. 7;

Fig. 6 is a section on the line 6 6, Fig. 7;

Fig. 7 is a partial section on the line 1 1, Fig. 2;

Fig. 8 is a top viewof the special tuning fork used in the constant frequency-generator;

Fig. 9 is a side view of the tuning fork;

Fig. 10 is an end view of the tuning fork, taken y from the right in Fig. 9;

The strobopreferably rubber.

Fig. 11 is a section through the crystal microphone unit associated with the tuning fork, taken on the line I I I I, Fig. 12;

Fig. 12 is another section through the crystal unit, taken on the line IZ-IAZ, Fig. 11; and

Fig. 13 is a circuit drawing showing in diagrammatic form the complete watch timing apparatus. v

Referring particularly to Figs. 1, 2, and 3, the timer is mounted on a base I, which may be a brass plate, provided with supports such as 2, The reference character 3 indicates a casing, which may be of sheet metal. The casing is provided with a cover 4 and is open at the bottom, where it ts closely around the base i. Small brackets 5 may be provided, spot welded in the inside of the casing. These brackets rest on the base I to which they may be attached by screws to hold the casing in place.

In the front of the casing there is a curved opening or window 6 the edges of which are turned inwardly as seen in Fig. 3. Behind the window is a wide metal strip 1, shown in dotted lines in Fig. 1, and seen in Figs. 2 and 3. This strip 'I is secured to the inside of the casing at so that it can be seen through the window 6.'

The front of the casing also has mounted on it a starting switch 9.

Inside the casing and supportedon the base I is a unitwhich comprises a synchronous motor, a dial, and an electro-magnetic device controlled by the beats of a watch being tested for rotating the dial. All of these parts are supported onA a'frame comprising the two horizontal plates I1 and I 8 and the vertical plates I0, Il, and I2. The plate I2 is held in position at the lower end by screws which are threaded into the plate I1, and plates I0 and II are secured at the lower end by means of'similar but longer screws which pass through holes in the vertical plates and in the horizontal plate I8, and are threaded into the plate I1. At the top the plates IIJ and II are spaced apart by two rods or bars I3 and I4 to which the plates are attached by means of screws, as shown. Similarly, plates II and I2 are spaced apart by means of two bars I5 and I6, being held in position by screws which are threaded into the bars. This affords a substantial frame for rigidly supporting the rotating parts of the unit. The frame rests on the base plate I to which it maybe attached by means oi' screws, as shown in Fig. .3.

The synchronous motor is similar to the motor shown in my co-pending application Ser. No. 124,571, filed February 8, 1937, except that it runs at higher speed and accordingly has fewer teeth in the armature. It comprises a shaft 20, armature 24, eld magnet 28, and y wheel 26. The shaft 20 is rotatably supported in the frame plates I0 and II by ball bearings 2| and ,22. The armature 24 is pressed onto a hub 23 which may be secured to the shaft 20 by a set screw. The field magnet 28 is preferably of laminated construction, as shown, and is provided with a winding 3l. The magnet is mounted on the frame plate I0 by means of two small bolts 29 and 30, there being two tubular spacers 32 and 33 inserted between the magnet and the frame plate I0 in order to position the magnet properly in alignment with the armature 24.

The fly wheel 26 is pressed onto a hub 25 which is rotatable on the shaft 20. A spiral spring 21 provides a flexible connection between the flywheel and the armature 24. The function of the fly-wheel is to enable the armature to fall into step at synchronous speed when the motor is started, andto this end it has the proper natural frequency of oscillation about the shaft 20 as determined by its weight and the stiffness of the spring 21.

'Ihe motor is started by means of a rack and pinion device which will now be described. On the outside of the frame member Ill thereis secured a bracket 65, which has the downwardlyextending end portions 66 and 61. These end members are perforated to provide bearings for the rack member 68', seen in Figs. 2, 3, and 4. ,This rack member has a toothed section on its lower side which is adapted to engage with the pinion 14 mounted on the end of shaft 20. The rack member 68 is urged to the left, as seen in Fig. 4, by means of a coil spring 69. This spring is stretched between a bracket 19 attached to the casing and the downwardly-extending arm 1I, which is part of the rack member 68. For the purpose of operating the rack there is provided a resilient rod 12 extending outside the casing and having attached to it a knob 13.

The dial is indicated by the reference character 62 and comprises a metal disk having three pointers, such as 80, spaced 120 apart. as shown in Fig. 1. The dial is mounted on a hub BI, Fig. 7, which in turn is carried on a shaft 52 to which it may be secured by a set screw. The shaft 52 is rotatably supported by means of two ball bearings 54 and 55 which are located at opposite ends ofthe sleeve or cylinder 53. The latter is threaded into an opening in the frame plate I2 and is locked in position by a nut 56. Between the hub 6I and the sleeve 53 is provided a cylindrical bushing 51, an ordinary washer 58, and a special spring washer 59, the latter having a number of radial 'arms or projections 60 which bear against the end of the sleeve 53. The bushing 51 is locked on the shaft 52 by means of a set screw, and the two washers accordingly con- 52, which will change the tension in the spring washer 53.

As seen particularly in. Fig. 3, the parts'arc so proportioned that the dial 62 rotates between the window G in the front of the casing and the scale 8. The diameter of the dial is such' that it is wholly concealed behind the casing except for the pointers such as 8D, one of which is always visible through the window, as shown in Fig. 1.

The electro-magnetic device by which the dial is controlled may now be considered, Fig. 7 being referred to in particular. This device comprises the armature 5I mounted on the dial shaft 52, and the electro-magnet 46 which is mounted on the-motor shaft 20.

The shaft 20 extends through the ball bearing 22 to the left, and has rigidly secured to it the rings 31 and 38.

hub 35, which comprises a head portion to which the disk 43 is secured and a cylindrical portion of reduced size on which are mounted the slip Between the slip rings and the hub thereis a tube or sleeve 36 of insulating material. These parts may be held together by friction; that is, the tube 36 may be forced onto the hub and the slip rings should have a press t on the tube 36. j

Associated with the slip rings are two brushes 39 and 40 which are clearly shown in Figs. 6 and 7. Brush 39 is secured to the frame plate I I by means of a screw 4| which is threaded into an insulated tubular rivet, as shownclearly in Fig. 1. This brush is in engagement with the slip ring 38. The brush 4!) engaging the slip ring minals 9| to 94, inclusive.

40 may be connected to terminals 93 and 94,'

31 is similarly secured to the frame plate II by means of the screw 42. As shown in Fig. 6, the brushes may be provided with offset lugs or tags for the attachment of conductors.

The electro-magnet 46 is preferably of laminated construction and is provided with a winding 41. The magnet is held in position between the legs of two U-shaped brackets 44 and 45 which in turn are attached to the disk 43 by means of screws as shown. As previously mentioned, the disk 43 is rigidly secured to the hub 35. The winding 41 is connected across the slip rings 31 and 38, as shown particularlyin Figs, 3 and '1. As seen in Fig. 3, one end 49 of the winding is provided with a suitable insulating sleeve and is passed through a 4hole drilled in the disk 43, hub 35 and slip ring 31, and is soldered to the slip ring 38. The other end of the rotation, except as limited by the friction device including the spring washer 59.

To facilitate the attachment of a cable for connecting the timer with the remaining apparatus. a terminal strip may be provided, having ter- The brushes 39 and while the winding 3| of the motor may be connected to terminals 9| and 92. One end of the V"minal strip I4 winding is connected direct to terminal 9|, and the other end of the winding is connected to terminal 92 through the switch 9. The cable may enter through an opening in the rear of the casing, and the four conductors of which it is composed may be connected to the terminals on the side opposite to where the brushes and winding 3| are connected.

Summing up all the foregoing, it will be seen that the timer includes the synchronous motor which is adapted to drive the shaft 20, carrying the magnet 46, there being slip rings mounted on the shaft to accommodate the magnet circuit, and thevdial 62 which is rotatable against-the resistance of the friction washer 59 and which is adapted to be rotated by the armature 5| cooperating with the electromagnet 46. The manner in which these parts operate will be described more in detail later on.

Reference will now be made to Figs. 8 t0 l2, inclusive, for the purpose of describing the tuning fork which forms a component part of the constant frequency generator. I'he complete tuning fork, so-called, includes the fork proper, a driving magnet,a crystal pickup unit, a terminal strip, and a suitable base on which the parts are mounted.

The fork comprises the tines |04 and |05 and the heel |06, and may be cast in the form shown,

, substantially independent of temperature changes over a wide range. The tines |04 and |05 are 'provided with weights |01 and |08, respectively,

for convenience in tuning the fork at the factory. These weights need not be adjusted afterwards, except under unusual circumstances.

The base |00 for supporting the fork and other parts is preferably a casting in the form shown, and has a pedestal |02 at one end on which the fork is mounted. The top of the pedestal has a shallow groove or recess to receive the heel |06 of the fork, which is held securely in place by means of two screws |03.

The drive magnet is indicated by the reference character ||3 and is preferably of laminated construction. The magnet has a winding I I1 and 'rubber bushing surrounding the pin |43.

comprising the two metal plates |30 and |33 andthe rubber rings |3| and |32. The construction of the receptacle is clearly shown in Figs. ll and 12. The crystal is supported by six rubber blocks such as |52, three above and three below. The terminal strip |5| passes out between the rubber rings |3| and |32, asseen in Fig. 11. The terminal strip |4| `is bent, as shown in Fig. 12. and is assembled between the ring |32 and the metal plate |33. It is cut off short enough so that it does not pass outside the receptacle. The pin |43 passes out through an opening in plate |33, this opening being provided with a soft The receptacle with the crystal contained therein is subjected to compression afterassembly, and the plates |30 and |33 are then secured together by means of four tubular rivets |44|`41. Thus the terminal strips are clamped in position and the crystal is resiliently supported at three corners by the rubber blocks |52, which are compressed between the plates |30 and |33.

The complete crystal unit 2| is mounted adjacent the tuning fork on a support |20, to which it is secured by means of four screws such as |48, as seen in Figs. 8 and 9. The support |20 may be cast as part of the base |00. The pin |43 is cut off to the proper length so that when the unit |2| is in position the pin will just reach the tine |05 of the fork. A spot on this tine has previously been tinned, so that the end of the pin is readily secured tothe tine by adrop of solder.

A terminal strip `is indicated by reference character |6I, and comprisesa fiat strip of fiber v||i| and four terminal lugs |62-|65. 'I'he strip is secured to the base |00 by means of two screws |66 and |61. Two tubular spacers |68 and |69 may be inserted between the strip and the base. The terminal |5| of the crystal unit may be connected to terminal lug |62. The other termitwo pole pieces ||4 and ||5. The pole pieces are secured to the core by means of small screws which also serve to hold the laminations toa gether at the ends. The magnet is supported by means of two small posts |09 and ||0 which are part of the base, and is'rigidly secured to these posts by means of bolts and I2.

The pickup device is a crystal microphone unit |2|, which is similar to the crystal unit disclosed in my prior application, Ser. No. 124,570, filed February 8, 1937. The so-called crystal which constitutes the operative element of the microphone unit comprises two square' sheets or plates |36 and |31, Fig. 12, of Rochelle salt, cemented together with a layer of tin foil |36 between them. There is also avlayer of foil |34 on one -side and a layer of foil |35 on the other. There is a thin strip of brass assembled next to the central foil |38, and underneath the foils |34 and |35 are assembled thin brass strips |39 andl |40, respectively. The brass strips |39 and |40 are directly opposite one. another, and their ends are brought together and are soldered to the ter- The brass strip |50 is soldered to a terminal strip 5|. At one corner of the assembled crystal there is cemented a member |42, to which is attached a short pin or rod |43.

The crystal is contained in a sealed receptacle nal |4| is grounded on the frame, and the frame is therefore connected to lug |63 by a short conductor secured under the head of screw |61, unless the Ybase is otherwise grounded. The terminals |62 and |63 therefore are the output terminals for the crystal unit. The winding may be connected to terminals |65 and |64.

The tuning fork is driven by impulses generated responsive to the ticking of a master watch, as will be explained presently, but for various reasons the frequency of the fork must be considerably higher than the beat frequency of the watch, which is ve cycles per second.

tained even with the best apparatus available are unsatisfactory. Another consideration that renders a higher frequency essential is the hunting that is always present in a synchronous motor. With a very low frequency, on the order of five cycles per second, the number of poles on the motor is so lowthat the hunting makes a watch timing apparatus inoperative for all practical purposes. The frequency must not be so high, however, as to make it impracticable to drive the fork from the beats of the master watch, and it must of course be an exact multiple of the beat frequency. Experiments have shown that the foregoing conditions are met satisfactorily if the fork is tuned to a frequency of 60 cycles vper second. The fork is so designed that its natural frequency is very close to 60 cycles, and it is then tuned exactly by adjusting the weights |01 and |08.

Referring now to Fig. 13, the timer and tuning fork, already described in detail, are shown diagrammatically within the dotted enclosures labeled T and F, respectively. The timer is a unit by itself. as shown in Figs. 1 to 7, inclusive. The tuning fork is also a complete unit, but is preferably mounted along with other items in a large casing which may be referred to as a power cabinet. These other items include the amplifier AI, the voltage. regulator VR, the power amplifier PA, the power supply unit R, and the amplifier A2. As the power cabinet may be of any suit- ',a-ble design and construction, such as is commonly used to house amplifiers, radio sets, etc., it has not been shown.

The microphone 200, used for picking up the beats from the master watch, may be mounted in the power cabinet in a shockproof compartment, as shown in my copending application Ser. No. 124,571, med February a, 1937. This microphone, as well as the test watch microphone 260, is preferably of the type shown in my Patent No. 2,175,021, granted October 3, 1939. This latter application shows the microphone cornplete with stand and cord for connecting it up to an amplifier. If desired, the stand may be enlarged so as to include the compartment for the master watch microphone; and if this is done, a single two-conductor cord will suflicefor connecting both microphones to the power cabinet. This cord, it will be understood, should be provided with a metallic sheathing in order to shield the conductors and ground the casings of the microphones.

The amplifier AI comprises a type 57 pentode 202, a type 6C8G double triode 203, and a type 885 thyratron 204. The tubes mentioned have been used in practice and operate very satisfactorily, although it will be understood thatl other types of tubes which are on the market could also'be used. y

The circuit connections for the pentode 202 are similar to those shown in my prior application hereinbefore referred to, but may be described briefly nevertheless. One side of the crystal unit in the microphone 200 is connected to the casing and thence to ground, as shown, and the other side is connected over a conductor to the grid of the pentode. The conductor 20| -should be shielded as previously mentioned. The plate of the tube is connected to the plus B lead through a resistor 2|0. The suppressor grid, the grid next to the plate, is connected to the cathode, and the latter is connected to ground through a resistor 201, which is an arrangement commonly employed to provide a negative grid bias. The resistor 201 is shunted by a by-pass condenser 208. The screen grid of the tube is connected-to the plus B lead at a point between the two bleeder resistances 210 and 21|, so that the voltage at the screen grid will be somewhat less than the voltage at the plate. The control grid is connected to ground through a high resistance grid leak 206.

The plate circuit of the pentode 202 is coupled to the grid of the left triode of tube 203 by means of a condenser 2| The' tube 203 constitutes in effect two ordinary triodes with conventional circuit connections which need not be described in detail. The plate of the left-hand triode is coupled to the grid of the right-hand triode through a condenser 2|3 and the potentiometer 2 |2. The

latter functions as a grid leak for the grid of the right-hand triode and also as a volume control.

The plate circuit of the right-hand triode of the tube 203 includes the resistor 2|4 and is coupled to the control grid of the thyratron 204 by means of the condenser 2|5. This control grid is provided with a negative potential over a conductor 251 and through the resistance 2|6, sutilciently to normally bias it to cut oi condition. The plate circuit of the thyratron includes the winding ||1 of the tuning fork drive magnet ||6 and the condenser 2|1, the latter being shunted by the high resistance 2|6. The condenser is therefore normally discharged, and is in condition to charge over -a circuit including the thyratron 204 and the winding ||1 whenever the tube has its grid bias lowered enough to' enable it to pass current.

The voltage regulator VR includes a type 6C8G double triode with the circuit connections as shown. The left-hand triode functions as an amplifier, while the right-hand triode functions as a voltage regulator. The crystal unit |2| of the pickup device at the tuning fork is resistance coupled to the grid of the left-hand triode. One terminal of the crystal unit is connected to ground, as shown, while the other terminal is connected to ground through the two resistors 2|9 and 220 in series. These resistors may have a value of 150.000 ohms each. The junction of the two resistances is connected to the grid of the lef t-hand triode.

The plate of the left-hand triode isconnected to the plus B lead through a resistor 22|7 and the plate circuit is coupled to the grid of the righthand triode by means of a condenser 223 and a resistor 224. The condenser 223 may have a capacity of .25 mf., while the value of the resistor 224 should be very high, preferably about 5 megohms. The junction point 0 between the condenser 223 and the resistor 224 is connected to ground through the grid leak 225, which may have a value of 500,000 ohms.

The plate circuit of the right-hand triode is connected to the plus B lead through a resistor 226 of about 50,000 ohms and a lter circuit comprising the inductance 221 and the condenser 228. The capacity of the condenser and the value of the inductance are such that the filter circuit is sharply turned to cycles. The filter circuit is coupled by means of a condenser 229 to the output lead 262 leading to the power amplifier.

The power amplifier comprises an ordinary triode 240 and two type 6N'7 double triodes 24| and 242.

y age regulator VR is coupled to the grid of the triode 240 by means of a'potentiometer 235, which constitutes an adjustable grid leak and is used as a voltage control. The plate circuit of the triode 240 is coupled push-pull to the grids of the double triodes 24| and 242 by means of the transformer 243. It will be observed that the two grids of tube 24| are connected in parallel and that the two plates are also connected in parallel, the same being true of tube 242. The plate circuits of tubes 24| and 242 are coupled by means of the transformer 244 to the output leads 263 and 264, which lead to the timer T. At the timer these conductors lead to the winding 3| of the synchronous motor, the circuit including a contact on the switch 9. v l

The amplifier A2 is similar to the amplifier AI and hence is not shown in detail, being represented merely by a rectangle in which the outgoing and incoming conductors are terminated.

The output lead 262 coming from the volt- The amplifier A2 may in fact be exactly, like the amplifier AI except that the condenser corresponding to the condenser 2|1 and the resistor corresponding to resistor 2|8 do not havel the same values. This will be explained later on in describing the operation of the equipment. The two output leads 261 and 268, which correspond to the output leads 265 and 266, respectively, of the amplifier AI, extendl to the timer T and through the slip rings 31 and 38 tothe winding 41 of the electromagnet 46. One side of the circuit includes a contact of the switch 8.

As shown in Fig. 13, the equipment is arranged to be operated from some alternating current commercial power source, and to this end a plug P may be provided which can be inserted in any convenient socket on 'the premises. The reference character 'S represents a main switch by means of which the power circuit is extended from the plug through to the primary winding 25| of the transformer 245.

The transformer 245 is included in the .power supply unit R and has a number of windings, the function of which will be mentioned briefly. 'I'he winding 250 supplies current to the heaters of the various tubes shown throughout the drawings including those in the two amplifiers A| and A2 and in the voltage regulator and the power amplifier. The heater circuits have not been drawn in, but it will be understood that each heater circuit which is labeled X--X is in practice connected to the terminals X-X of the winding 250, a suitable resistor being included in the heater circuit of tube 202 in order to limit the current to about one ampere.

The main rectifier` tube 253 is connected for full wave rectification and has the function of supplying plus B potentials to the various tube circuits. The two plates of the tube are connected to the opposite terminals of the winding 248. The midpoint of this winding is grounded and constitutes the negative terminal of the power supply unit. The cathode of the tube is supplied with heating current from the winding 249 f the transformer and is connected through asuitable filter to the various plus B leads, as illustrated. The highest voltage is supplied to the lead 259 over which power is supplied to the plates of the tubes 24| and 242 of the power amplifier. A somewhat lower voltage is supplied over the conductor 254 to the plate of the amplifying triode 240, and a still lower voltage is supplied over leads 255 and 256 to the two amplifiers A| and A2 and to the plates of the tube 205 in the voltage regulator VR.

The rectifier tube 252 is also connected for full wave rectification and is provided for the purpose of supplying negative grid bias potential to the thyratrons in the amplifiers AI and A2. The cathode of the tube is heated by means of the winding 241 of the transformer 245 and is connected to ground. The two platesl of the tube are connected to the opposite terminals, respectively, of the winding 246 of the transformer 245. The midpoint of this winding constitutes the negative terminal of. the rectifier and is connected through a suitable filter circuit to the conductors 258 and 251.

the gridof the thyratron 204 in the amplifier AI, and the conductor 258 is similarly connected in the amplifier A2.

The apparatus having been described, its operation in timing watches will now bevexplained. It may be assumed that a master watch which The conductor, `251 is connected through the resistor 2|6 to has been previously regulated to keep correct time is clamped to the microphone 200. The master watch should be a five-beat watch and should be adjusted so that the successive beats are evenly spaced. A high grade watch is obviously desirable, and the more perfect its regulation the better, but it need not be regulated for various positions.

The first step on starting up the apparatus is to insert vthe plug P, Fig. 13, in a convenient socket connected to commercial A. C. power,

after which the switch S may be closed. As a result, power is supplied to the unit R, and the latter functions to supply heating current to the variousitubes and to supply power for the plate circuitsof the tubes over the plus B leads. The requisite negative 'potential is also placed on the grid bias leads 251 and 258. The amplifiers are thus rendered active and ready to perform their respective functions.

The master watch being in position on the microphone 200, at each beat or tick of the Watch, a mechanical shock istransmitted to the crystal element in the microphone, in response to which the crystal element generates an electrical impulse, which is transmitted over the conductor 20| to the grid of the amplifying pentode 202. The impulse is amplified at the `pentode 202 and is passed on through the condenser 2|| to the grid of the left triode of the double triode 4203, where itis further. amplified.

The plate circuit of the left triode being coupled to the grid of the right triode through the condenser 2|3, the impulse is amplified once more, and is then transmitted through the condenser 2|5 to the grid of the thyratron 204 where it reduces the normal negative grid bias enough so that the tube can fire. The action is not as simple as this, in reality, but it is well understood and hence it wil1 not be necessary to go into details.

When the thyratron fires, or starts'topass current, the condenser 2|1 charges over a circuit which may be traced from ground bry way of the cathode and plate of thyratron 204, winding I1, and condenser 2|1 to the plus B lead 255. `The condenser 2|1 charges rapidlyl over the above circuit and as a consequence the current flow through the tube 204 falls rapidly toward a value determined by the high resistance 2 I8, which extinguishes the tube. The condenser then discharges through the resistance 2 8 in preparation for charging again the next timethe thyratron res. v

The charging current of the condenser flows through the winding ||1 offthe tuning fork drive magnet H6, as per the circuit above traced, and accordingly the magnet is energized. attracting the tines |04 and |05 of the tuning fork and pulling them apart. The energization of the magnet ||6 is of very short duration. `When the tines are released they start vibrating vat they natural fork frequency. or 60 cycles per second. The next time the condenser 2|1 charges the magnet ||6 is energized again, giving another pull to thefork tines. T his action is repeated responsive to each beat of the watch, or five times per second, and the fork is very shortly brought up to full amplitude of vibration.

It is essential that the duration of the impulses delivered to the magnet ||6 by the charging ofthe condenser be properly related to the fork frequency in order to secure a' satisfactory drive. 'I'he magnet is effective to drive the fork only when the tines are moving away from each other, or toward the magnet poles, and as the frequency of the fork is 60 cycles per second, this movement takes place in ho of a second. It has been found by experiment that excellent results are secured if the impulses delivered to the fork are about y; of this interval, and the capacity of condenser 2H is therefore so related to the impedance of winding II'I that the condenser Y i will charge up enough to extinguish the thyratron in about $480 of a second.

The winding H1 and the condenser 2 l l are therefore so designed as to give the proper length of drive impulses, and this may be done before taking into consideraiton the proper response of the thyratron to the watch beats. This latter is taken care of by properly regulating the value of the resistance 2I8. This resistance should be low enough so thatit will substantially discharge the condenser 2H between watch beats, or in 1/5 of a second, and it should be high enough so that the condenser cannot discharge' fast enough to permit the thyratron to fire a Vsecond time responsive to the same watch beat.

It will be seen now that at each beat of the master watch an impulse is produced which is amplified by the tubes 202 and 203 and which is effective to trigger the thyratron and permit the condenser 2I1 to charge through the tube and the winding H1 of the drive magnet. The impulses thus transmitted to the drive magnet, being derived from the master watch, have a frequency of exactly five per second, or 1/12 of the fork frequency, and therefore are in step with the fork and serve to maintain it in operation. This is not to say that the fork must have a frequency of exactly 60 cycles per second, although it is tuned as nearly to that frequency as possible. A variation of as much as three or four minutes per day in fork frequency is permissible. When-the fork is slightly off, either fast or slow, a correction takes place ve times per second, or :.t each drive impulse. l

The exact manner in which the correction takes place is difficult to determine, although careful observations have been made. If the fork h as exactly the proper frequency, the drive impulse is apparently delivered as lthe tines are nearly separated the maximum extent and is terminated slightly after the tines come to rest before starting to approach each other. Now, if the fork is too fast it will gain on the drive impulses, and the tines will start to approach each other on each drive impulse enough before the impulse is completed so that it can exercise a slight retarding effect. On the other hand, if the fork is too slow; the drive impulses will gain on the fork, and each drive impulse will come in at a time when it can deliver more power to the fork than it could if the fork had exactly the right frequency, with the result that the fork is accelerated. This explanation of course Yimpulses that the drive impulses have considerably morepower than is necessary to drive the fork when exactly in tune,'which is the case. It may be mentioned also that if the fork is considerably off as to its frequency, although not enough to prevent it from running in step with the master watch, its amplitude will be' reduced. This, however, is prevented from having any deleterious effect by the voltage regulator, as will bel presently explained.

The vibrations of the tuning fork are transmitted to the crystal microphone l2! by the pin |43, as is evident from Fig. 8, and the microphone generates a (iO-cycle alternaitng current in a coupling circuit including resistances 2I9 and 220,

whereby alternating potentials are applied to the grid of the left triode of the double triode tube 205. As a result, the plate current fluctuates and the voltage on the plate of the left triode rises and falls. This causes the condenser 223 to charge and discharge' in series with the resistor 225, and alternating voltages are produced at the point 0 in the condenser circuit. These potentials vary in amplitude, depending on the amplitude of the voltages applied to the grid of the left-hand triode, which in turn depend on the tuning fork amplitude, and it is the function of the right-hand triode to limit the effect of both the positive and the negative half waves and maintain a uniform output within certain limits independent of the strength of the impressed voltages.

The effect of the negative potentials is limited byV proper adjustment of the grid bias of the right-hand triode. This grid bias is adjusted so that with a negative half wave of the minimum strength some current will still ow through the tube; but if the signal strength is increased somewhat, producing voltage changes at the point 0 of higher amplitude, the negative half waves will bias the tube to cut off, and no current will flow during the peak values of such negative half waves.

The positive half waves are limited as to their effect by means of the resistor 224, whichls in series with the grid. This resistance has no effect during the negative half Waves, as the grid is drawing no current, but when the grid swings positive it draws current through the resistor 224. The resistor 224 is very high, being about 5 megohms, and consequently the drop is so high that the potential on the grid can rise only an infinitesimal amount. The' result is that no matter what amplitude the positive half wave voltages at the point 0 have, the grid can never become more thanal fraction of a voit positive, and the current through the tube is definitely limited to what can ow with this grid potential.

It will be seen therefore that the right triode of tube 205 operates as a. voltage regulator and supplies a 60-cycle output of substantially uniform voltage independent of the amplitude of the tuning fork. When the fork has the minimum amplitude for which the circuit is adjusted, the output of theright triode of tube205 will be approximately a sine wave, but with increasing amplitudes the voltage-regulating characteristics come into play and the output has a flattened wave formation.- In order to correct this, the plate circuit includes a resonant circuit comprising the condenser 228 and inductance'221 which is tuned to 60 cycles per second. This tuned circuit is coupled to the output lead 262 through a condenser 229, and the voltages 0n this outputv lead are of excellent wave form, approximating a sine wave, and are of substantially uniform voltage, irrespective of varying fork amplitudes amplifier AI in order to secure a regular firing of the thyratron 204 responsive to the beats of the master watch. The potentiometer 235 is used to adjust the output voltage of the power amplifier to the desired value. When once adjusted these controls need no attention for long intervals. v

' The switch 9 may now be closed, thereby bridging the field winding 3| of the synchronous motor in the timer T across the output leads 263 and 264. The motor is started by pulling out the knob 13 and releasing it. When the knob is pulled out, the rack 68 is moved to the right, as seen in Fig. 4, and tension is stored in the spring 69. At the same time the teeth on the rack engage the pinion 14 and rotate the shaft 20, This rotation, however, is merely incidental to the starting operation. When the knob is released, 'the spring 69 draws the rack rapidly to the left and rotates the pinion 14 in the opposite direction. This spins the armature 24 rapidly, at aspeed which is somewhat higher than synchronous speed. When the rack reaches its lefthand position as shown in Fig. 4, the teeth are disengaged from the pinion and the armature is allowed to run free. It therefore slows down gradually to synchronous speed at which point it falls into step with the assistance of the flywheel 26.

If the teeth of the rack do not properly engage the pinion when the knob 13 is pulled out, the rack will rise slightly at the right-hand end, as seen in Fig. 4, such action being provided for by the resiliency of the rod 12 and by the enlarged opening .in member 66 which provides a little play above the rack. The spring 60 pulls slightly downward on they rack which insures that the teeth will engage when the knob is released, if

not before.

The synchronous motor in the timer T is now Abeing driven by the master watch through the intervening apparatus including the beat amplifier AI, thev tuning fork F, the voltage regulator VR, and the power amplifier PA. 'I'his apparatus serves to convert thefive-cycle beat frequency output of the microphone 200 into an amplified 60-cycle current having power enough to run the motor. The motor runs at five revolutions per second, and to this end the armature 24 is provided with twenty-four teeth. By means of shaft the motor rotates the magnet 46 in a counter clockwise direction, as viewed from the front of the timer. The dial 62 is stationary.

A watch to be tested may now be clamped to the microphone 260. It may be assumed that the watch is a five beat watch. The microphone responds to the Watch beats and generates impulses which are amplified by the amplifier A2 and are effective to control the thyratron in thisamplier in the same manner as described in the case of thyratron 204 in amplier Al. The plate circuit of the thyratron includes the two output leads 261 and 268, corresponding to leads 265 and 266 of amplifiers Al; and when the thyratron fires the -condenser which corresponds to condenser 2l1 charges over a circuit which includes the cathode and plate of the thyratron, lead 261, winding 41 of magnet 46, switch 9 (now closed), lead .268, and the condenser. As soon as the condenser becomes substantially charged, current ow is reduced sufliciently to extinguish the thyratron, and the condenser then discharges through' a resistance corresponding to resistance 2|8. The action is the and condenser 241, except that the capacity, impedance, and resistance values are so chosen that the impulses delivered to the magnet 46 are much shorter than those delivered to the drive magnet IIS of the tuning fork. Impulses not over l/isoo of a second in duration give good results. l

It should be recalled now that the magnet 46 is rotating in a counter clockwise direction at a speed of flve revolutions per second. The first impulse received will come in at a time when the magnet 46 is in some random position relative to the armature 5|. If the magnet and armature are in the position iny which they are shown in Fig. 5, no rotation of the armature will ensue; but if the magnet is in such a position that the magnet poles are not in alignment with a pair of armature poles', the nearest pair of armature poles will be attracted and the armature will be rotated. This rotation is opposed by the resistance developed at the friction device including the spring washer 59, and by the inertiaof the armature 5|-and dial 62, and the adjustment is such that, having regard to the very short duration of' the impulses, ther maximum amount of rotationl that can take place rey sponsive to a single impulse is about four or' y position relative to the armature, each time the ing of the armature relative to the rotating magsame as described in the case of thyratron 204 net and is disregarded. If the test watch is keeping correct time, no further movement of the pointer will occur, and the operator knows from this that the watch is correct.

Assuming now that the test watch is running too slow1y,. the rotating magnet will gain on the impulses which it receives from the test watch and will rotate slightly more than a complete revolution between successive impulses. As each impulse is received, therefore, the magnet will be in a slightly advanced position where it can exert a pull on the armature, tending to rotate the dial and pointer in a counter clockwise direction. The pointer 80 will therefore move gradually to the left as seen in Fig. 1, indicating to the operator that the test watch is running slow.

Assuming, on the other hand, that the test watch runs too fast, the impulses delivered to the rotating magnet 46 will gain on the magnet, which will make somewhat less .than a complete rotation between successive impulses. As each impulse is received, therefore, the magnet will be in a retarded position relative to the armature and will rotate it in a clockwise direction, moving the pointer 80 to the right, as seen in Fig.- 1.

Such movement of the pointer indicates to the operator that the test watch is too fast.

The amount by which the pointer drifts to the right or left within a given time determines how much the test watch is too fast or too slow. In order to facilitate the timing operations, the scale 8 is preferably laid out with such a spacing between divisions that if the scale were continued around a complete circle there would be 96 scale divisions. Each scale division will then correspond to a gain or loss of three seconds per day ona test of one minute duration. In timing a watch `the operator notes the position of the pointer 80 after the initial positioning movement has taken place and then allows the apparatus to run for one minute, when the new position of the pointer is noted. If the pointer moves four scale divisions during the one minute interval, this means that the test watch is twelve seconds per day fast or slow, depending on the direction of the movement.

The error in seconds per day, which corresponds to a drift of any number of scale divisions during a one minute test, may be calcul lated from the proportion in which n=drift in scale divisions, dp1n=rota tional speed of magnet 46 measured in scale divisions per minute, .'r=error in seconds per day, and 86400=number of seconds in one day.

For the case of the particular timing apparatus disclosed herein the quantity dpm is equal to 28800 (5X60X96), and the proportion may be reduced to an equation ior :r in the form From this equation it will be seen that if the drift in one minute is one scale division, forl example, the error .is equal to three seconds per day.

Six beat watches may be tested in the same manner as ve beat watches. The apparatus operates the same except that the impulses received by magnet 46 will have a frequency of six per second instead of five per second and will gain on the rotating magnet at the rate of one-sixth rotation per impulse. The armature 5I has six poles, and the magnet 46 will therefore lag behind each impulse a distance of exactly one pole spacing, and will operate on successive pairs of poles instead of on the same pair each time.

The apparatus has been shown herein as operating from a source of commercial alternating current, but obviously will operate from direct current, If a suitable source of direct current is available the power supply unit R can be dispensed with.

The timer disclosed herein has numerous advantages and is to be highly recommended, but is not absolutely essential. Other forms ol timing apparatus can be used if desired. For instance, the timing apparatus described in my pending application Ser. No. 124,571 may be used. When this is done, the motor is driven by the master watch through the medium of the apparatus disclosed in the instant application, and the correcting mechanism is omitted entirely. The complete timing apparatus will then consist of the constant frequency generator as disclosed herein, the motor and dial of my prior application referred to, and the dial-illuminating means responsive to the beats of the test watch as also disclosed in my prior application. This makes a very simple and economical equipment suited to the use of those desiring the stroboscopic type of apparatus.

The invention having been described, that .which is believed to be new and for which the protection of Letters Patent is desired will be pointed out in the appended claims.

I claim as my invention:

1. Inra device for timing watches of different beat frequencies, an electromagnet, an armature operatively related to said electromagnet and having a number` of poles bearing a predetermined relation to the beat frequency of one watch, means i'or producing relative rotation between said magnet and armature at a speed bearing a predetermined relation to the beat frequency of the other watch, means responsive to the beats of the watch being tested for periodically energizing said magnet, and an indicator controlled by said armature.

2. In a timing device, a casing having an arcuate window therein, a rotatable member mounted inside said casing and having a plurality of indicators adapted to be viewed through said window, said indicators being angularly spaced the proper distance so that one indicator is always visible, a scale associated with said window, and means within the casing for rotating said member at a speed. dependent on the amount by for rotating said magnet at constant speed, and means responsive tov said impulses for causing momentary energizations of said magnet.

4. In a device for timing periodic impulses, indicating means comprising cooperating fixed and vrotatable members, the rotatable member having a plurality of equivalent angularly spaced parts, an armature for rotating said rotatable member and having a plurality of sets of poles, a magnet adapted to cooperate with a random pole set, means for rotating saidmagnet at constant speed, and means responsive to said impulses for causing momentary` energizations of said magnet, y

5. In a device for timing periodic impulses, a magnet, means for rotating said magnet at a constant speed, a normally stationary armature having a plurality of sets of poles adapted to cooperate with the poles of said magnet, means responsive to each impulse for causing a momentary energization of said magnet, the rotational speed of said magnet being such that it cooperates with successive adjacent sets of armature poles on successive energizations, and an' indicator moved by said armature in one direction tarily energize the/'electromagnet at intervals corresponding to the ticks, whereby the position of the armature is controlled by the ticks to give an indication of the rate thereof.

7. In apparatus of the character described, in combination, a rotatable member, an electromagnet carried by the rotatable member, means for periodically momentarily energizing the electromagnet, an armature mounted substantially conmeans for supporting said parts for independent' cluding two parts, one part comprising an electromagnet and the other part comprising an armature cooperating with said electromagnet.

5 rotation on a common axis, means for periodically momentarily energizing said electromagnet, means for rotating one of said parts'at a predetermined constant speed, and means for fric tionally normally-maintaining the other part at rest, the friction bein'g not so great as to prevent the said frictionally held part from moving into alignment with the other part when the electromagnet is momentarily energized but being suii'icient to prevent overrunning .Qf the said frictionally held part upon the termination of the momentary energization.

THOMAS B. GIBBS. 

